Last updated November 6, 2026
General information, not tax or legal advice. The rules depend on your country and your situation, so check anything with a tax or legal consequence with your accountant.
A billing increment is the smallest unit of time you charge. One unit is 0.1 hour in 6-minute billing, 0.17 in 10-minute billing and 0.25 in 15-minute billing. Round the minutes worked up to the next unit using the charts below, then multiply the decimal hours by your rate.
6-minute increment chart
The 6-minute increment is the cleanest of the three, because one unit is exactly a tenth of an hour. It's the traditional unit in law firms and is also common in accounting.
| Minutes worked | Units | Billed as (minutes) | Decimal hours |
|---|---|---|---|
| 1–6 | 1 | 6 | 0.1 |
| 7–12 | 2 | 12 | 0.2 |
| 13–18 | 3 | 18 | 0.3 |
| 19–24 | 4 | 24 | 0.4 |
| 25–30 | 5 | 30 | 0.5 |
| 31–36 | 6 | 36 | 0.6 |
| 37–42 | 7 | 42 | 0.7 |
| 43–48 | 8 | 48 | 0.8 |
| 49–54 | 9 | 54 | 0.9 |
| 55–60 | 10 | 60 | 1.0 |
10-minute increment chart
The 10-minute increment gives round minutes and awkward decimals, because a sixth of an hour never comes out exactly. The values below are rounded to two decimal places.
| Minutes worked | Units | Billed as (minutes) | Decimal hours |
|---|---|---|---|
| 1–10 | 1 | 10 | 0.17 |
| 11–20 | 2 | 20 | 0.33 |
| 21–30 | 3 | 30 | 0.50 |
| 31–40 | 4 | 40 | 0.67 |
| 41–50 | 5 | 50 | 0.83 |
| 51–60 | 6 | 60 | 1.00 |
15-minute increment chart
The 15-minute increment is the simplest to apply by hand, and usually the most generous to whoever is billing.
| Minutes worked | Units | Billed as (minutes) | Decimal hours |
|---|---|---|---|
| 1–15 | 1 | 15 | 0.25 |
| 16–30 | 2 | 30 | 0.50 |
| 31–45 | 3 | 45 | 0.75 |
| 46–60 | 4 | 60 | 1.00 |
For anything over an hour, count the whole hours and look up the remainder. So 1 hour 20 minutes is 1.40 in 6-minute billing, 1.33 in 10-minute billing and 1.50 in 15-minute billing.
The three increments side by side
This table shows the same minutes under each increment, rounded up, next to the exact decimal.
| Minutes worked | Exact hours | 6-minute | 10-minute | 15-minute |
|---|---|---|---|---|
| 5 | 0.08 | 0.10 | 0.17 | 0.25 |
| 10 | 0.17 | 0.20 | 0.17 | 0.25 |
| 15 | 0.25 | 0.30 | 0.33 | 0.25 |
| 20 | 0.33 | 0.40 | 0.33 | 0.50 |
| 25 | 0.42 | 0.50 | 0.50 | 0.50 |
| 30 | 0.50 | 0.50 | 0.50 | 0.50 |
| 35 | 0.58 | 0.60 | 0.67 | 0.75 |
| 40 | 0.67 | 0.70 | 0.67 | 0.75 |
| 45 | 0.75 | 0.80 | 0.83 | 0.75 |
| 50 | 0.83 | 0.90 | 0.83 | 1.00 |
| 55 | 0.92 | 1.00 | 1.00 | 1.00 |
| 60 | 1.00 | 1.00 | 1.00 | 1.00 |
A smaller unit doesn't always bill less. Fifteen minutes is 0.25 in 15-minute billing and 0.30 in 6-minute billing, because 15 falls just past a 6-minute boundary.
How much does the increment change the bill?
The increment can change a day's bill by a lot when the day is made of short tasks, because each entry rounds up separately. Here's an invented example: seven entries of 7, 11, 4, 22, 16, 9 and 38 minutes, 107 minutes in all, at €120 an hour.
| Rounding | Minutes billed | Hours | Charge at €120 | Above exact time |
|---|---|---|---|---|
| None | 107 | 1.78 | €214.00 | |
| 6-minute, each entry | 126 | 2.10 | €252.00 | €38.00 |
| 10-minute, each entry | 140 | 2.33 | €280.00 | €66.00 |
| 15-minute, each entry | 165 | 2.75 | €330.00 | €116.00 |
| 6-minute, day's total once | 108 | 1.80 | €216.00 | €2.00 |
The charges are worked from the minutes, which is why 2.33 hours shows €280.00 rather than €279.60. The next section explains that gap.
The 15-minute row bills over half as much again as the time worked. On long blocks of work the gap nearly vanishes, and on a day of quick calls a client reading the log could fairly object. The last row is an option worth considering if you want the tidiness of a unit without the build-up: round once, on the total.
Why do 10-minute decimals drift?
Decimals drift in 10-minute billing because 0.17 is itself a rounding of 0.1667. Six 10-minute entries at 0.17 add up to 1.02 hours rather than 1.00, so at €120 an hour you bill €122.40 for one hour of work.
The fix is to add up the minutes for each invoice line first, and convert once. In the example above, adding the seven rounded decimals gives 2.34 hours, while 140 minutes converts to 2.33. On an invoice that holds two decimals, 2.33 × €120 is €279.60.
Which billing increment should you use?
Use the smallest increment that's practical for how you work, and write it into your agreement.
| Increment | Usually suits | Trade-off |
|---|---|---|
| 6 minutes | Legal and accounting work, advice with many short tasks | More entries to keep, clean decimals |
| 10 minutes | Teams who prefer round minutes | Easy to read, drifts in decimals |
| 15 minutes | Site work, repairs, longer blocks of consulting | Simple, but overcharges on short tasks if every call rounds up |
A minimum charge is a separate term from an increment, so state it separately. "Minimum charge of one hour per visit" belongs on a call-out, and has nothing to do with how you round the rest.
Wording for the quote or contract:
We record time in units of 6 minutes (0.1 hour), and each entry is rounded up to the next unit. Time is charged at the hourly rate shown in this quote.
The guide to tracking billable hours explains why the raw minutes should stay in the log. Rounding belongs at the point where you turn hours into an invoice.
How do you round to an increment in a spreadsheet?
CEILING rounds minutes up to the next increment in both Excel and Google Sheets. With the minutes in cell A2:
| Increment | Formula | 7 minutes gives |
|---|---|---|
| 6-minute | =CEILING(A2,6)/60 |
0.2 |
| 10-minute | =ROUND(CEILING(A2,10)/60,2) |
0.17 |
| 15-minute | =CEILING(A2,15)/60 |
0.25 |
Using billing increments in ERPFlow
ERPFlow has no billing increment setting and doesn't round time. ERPFlow doesn't have a timer or timesheets today. Time tracking, including converting tracked time into invoices, is coming soon.
A card in Projects holds Time spent as the hours and minutes somebody typed, so converting to decimal is a job for the charts above. An invoice line then takes that figure as its quantity, usually from a service that holds your hourly price. The quantity holds two decimal places, so 6-minute and 15-minute values go in exactly. For 10-minute billing, add the minutes first and enter the converted total, such as 2.33.